The NA62 RICH detector

The NA62 experiment at CERN, aiming at a precision measurement of the ultra-rare decay K + → π + ν ν ¯ , relies on a gas based RICH detector for π / μ separation and level 0 trigger. The experimental requirements for this detector are a time resolution better than 100 ps and a muon rejection factor better than 5×10−3 in the momentum range 15–35 GeV/c. A first prototype of such a detector has been built and tested in 2007, as a first check of its time resolution and of the light collection technique; it consists in a full length (18 m) Ne filled vessel equipped with a spherical mirror and 96 PMs on its focal plane, ≈ 17 m upstream of the mirror. The prototype has been tested at CERN SPS on a 200 GeV/c pion beam mainly; the time resolution has been found to be about 65 ps, and the light collection, i.e. the number of hit PMs per ring, fairly as expected.